The transmission frame pursuant to the DVB standard utilizes the MPEG 2 Transport Stream. This transport stream is arranged with a consideration for transmitting a plurality of program signals by one stream, so as that the transport stream can utilize a plurality of reference times. The transport stream comprises a 188 byte fixed length packet (transport packet) including one byte synchronizing signal (hereinafter referred to as SYNC). In the DVB standard, MPEG 2 SYNC is used directly as a synchronizing byte of the transmission frame.
In the DVB standard, the transport stream is applied with the encryption, such as a scramble. In this case, the encryption is applied in a unit of a 188 byte length transport packet-basis.
In a receiver pursuant to the DVB standard, an IC card may be used for the decryption, such as a descrambling. It becomes possible to make a plurality of broadcast signal receivers commonly usable when the decryption is carried out using an IC card.
As an interface standard in the DVB standard, there is the Common Interface Standard (EN50221) which defines the interface format between receivers and IC cards. This standard defines the signal communication between the receiver main unit and an IC card in viewing a subscription TV channel wherein an encrypted broadcast signal, such as a scrambled broadcast signal is received by the receiver main unit and the decryption (decoding) is carried out by an IC card.
FIG. 1 is a block diagram showing a conventional digital broadcast receiver using such IC cards. Herein, a receiver main unit A101 makes possible for users to view broadcast program by demodulating signals such as a satellite broadcast signal, a CATV broadcast signal, etc., supplied to an input terminal A104 and then supplying the demodulated signal to a TV receiver.
Generally, there are two type of programs in a broadcast system, i.e., free program broadcasts and subscription program broadcast. In case of the subscription TV channel, the broadcast signal is encrypted by being encrypted in the broadcast station side and transmitted to the receiving apparatus side. When the receiving apparatus belonged to a subscription user receives the broadcast signal transmitted by being encrypted, it decrypted the broadcast signal by decrypting within the IC card loaded to the receiver main unit, so that it decodes the signal and supplies to the television receiver. Accordingly, the user is possible to view the broadcast program which is processed the encryption.
Concretely, to a turner/demodulator A105, shown in FIG. 1, the digital broadcast signal, which is frequency, multiplexed and time division multiplexed is supplied via the terminal A104. The tuner/demodulator A105 selects the signal with a carrier frequency corresponding to the program signal selected by viewers, at the same time it demodulates it and supplies to an error corrector A106. Generally, on the transmission of the digital broadcast the error correcting code is added to the program signal. Accordingly, the error corrector A106 corrects the error of the broadcast signal on its transmission channel. Generally, the signal stream supplied from the error corrector A106 has a format conformable with the MPEG-SYSTEM (ISO/IEC13818-1) standard, time-division-multiplexing thereon a plurality of program signals. The signal stream is supplied to the signal processor 116 (decryptor) defined in an IC card A102, which is connected to the receiver main unit A101. The decryptor A116 decrypts the signal stream, and then supplies the decrypted signal stream back to the receiver main unit A101.
The decryption of the stream signal in the IC card A102 is carried out over a necessary portion on the stream signal where the encryption is needed, however, it is not carried out over the necessary portion. That is, the IC card A102 decrypts only program signals assigned by viewers among the stream signal wherein a plurality of program signals are multiplexed. However, it supplies the other to the receiver main unit without decryption.
Here, in the digital broadcast receiver, it is possible to connect the several IC card according to the several subscription TV systems. The input and output signals between these IC cards are coupled with each other in so-called a daisy-chain fashion. That is, the output signal from the error corrector A106 is decrypted as needed by the decryptor A116 of the IC card A102, and supplied to a selector A107 in the receiver main unit A101, then it is supplied to the IC card A103 via the selector A107 and supplied to a selector A108 in the receiver main unit A101 by being encrypted as needed by the decryptor A117 of the IC card A103.
In FIG. 1, the decryptor is shown as the function of the IC cards A102 and A103. However, at least two IC cards may be connected in the daisy-chain fashion, further, the application of the IC card may be the teletext receiving function or the external output interface.
Each of the IC cards A102 and A103 communicates between a controller A113 inside the receiver main unit A101 via each of controllers A118 and A119 in order to control each of the descrablers A116 and A117.
When the broadcast signal which is carried out the signal processing (decryption) by each the IC cards A102 and A103 is supplied to the receiver main unit A101, a demultiplexer A109 (demultiplexer) selects the required signal among the time division multiplexed broadcast signal and supplies it to an audio/video decoder A110. The audio/video decoder A110 denotes the digital compression encoded audio/video signal and supplies it to an audio/video output processor A111. The audio/video output processor A111 carries out a D/A conversion and a system conversion and supplies the broadcast signal to the television receiver via a terminal A112. Accordingly, viewers can view his/her favorite broadcast program.
The IC cards A102 and A103 are removable to the receiver main unit A101, so that viewers use the apparatus by removably coupling several kinds of IC cards according to the purpose. The loading/unloading of the IC cards A102, A103 is detected by each of IC card detectors A114 and A115 in the receiver main unit A101. The controller A113 in the receiver main unit A101 then controls the selectors A107 and A108 in response to the detection outputs from the IC card detectors A114, A115.
Concretely, when the unloaded status of both the IC cards A102 and A103 are detected by the IC card detectors A114 and A115 (in the case of that the IC card is not put on the receiver main unit A101), the controller A113 controls the selector A107 in order to select the broadcast signal, at the same time, it controls the selector A108 in order to select the broadcast signal via the selector A107. Accordingly, since the broadcast signal is supplied to the television receiver without encryption, viewers may not view his/her favorite broadcast channel.
Further, when the unloaded status of the IC card A102 is detected only in the IC card detector A114 (in case of that only the IC card A103 is put on the receiver main unit A101), the controller A113 controls the selector A107 in order to select the broadcast signal supplied from the error corrector A106, at the same time, it controls the selector A108 in order to supply the broadcast signal via the selector A107 to the IC card A103. Then, it controls the selector A108 in order to select the broadcast signal which is encrypted by the IC card A103. Accordingly, the broadcast signal which is decrypted according to the IC card A103 is supplied to the television receiver, so that viewers can view his/her favorite broadcast program.
Further, when the unloaded status of the IC card is detected in only the IC card detector 115 (in case of that only the IC card A102 is put on the receiver main unit A101), the controller A113 controls the selector A107 in order to supply the broadcast signal supplied from the error corrector A106 to the IC card A102, at the same time it controls the selector A108 in order to select the broadcast signal supplied from the selector A107. Then, it controls the selector A107 in order to select the broadcast signal that is decrypted by the IC card A102. Accordingly, the broadcast signal that is decrypted corresponding to the IC card A102 is supplied to the television receiver, so that viewers can view his/her favorite broadcast program.
Further, when the unloaded status of the IC cards A102 and A103 are not detected in the detectors A114 and A115 (in case of that both the IC cards A102 and A103 are put on the receiver main unit A101), the controller A113 controls the selector A107 in order to supply the broadcast signal supplied from the error corrector A106 to the IC card A102, at the same time it controls the selector A107 in order to select the broadcast signal that is decrypted by the IC card A102. Then, the controller A113 controls the selector A108 in order to supply the broadcast signal supplied from the selector A107 to the IC card A103, at the same time, it controls the selector A108 in order to select the broadcast signal that is decrypted by the IC card A103. Accordingly, the broadcast signal that is decrypted to the IC cards A102 or A103 is supplied to the television receiver, so that viewers can view his/her favorite broadcast program.
By the way, the receiver unit A101 and the IC cards A102, A103 are coupled each other by loading the IC cards A102, A103 into the receiver main unit A101. Then it is possible to take out the received signal outside the receiver main unit A101 and the IC cards A102, A103, from connectors on the receiver main unit A101 or the IC cards A102, A103. In other words, digitized broadcast signals appear directly on the IC card interface portion between the receiver main unit A101 with the IC cards A102, A103 and therefore, there was the possibility that an unauthorized copying might be made.
Further, as it is so designed that IC cards feed the decrypted signal back to the receiver main unit A101, even in case of an encrypted subscription TV program, it is possible to extract the decrypted signal from the outputs of the IC cards A102, A103 and there was the possibility that the unauthorized copying might be made.
As described above, the conventional digital broadcast apparatus is used by removably coupling the IC cards A102 and A103 freely to the receiver main unit A101. Generally, as signal processors in IC cards, e.g., decryptors A116 and A117 reuire some length of time for processing signals, there is cused same amount of delay times between inputs and outputs of the IC cards A102 and A103. Accordingly, there are some phase differences between the signal supplied to the IC card and the signal supplied from the IC card. Further, when the selectors A107 and A108 select the broadcast signals directly supplied thereto or the broadcast signals processed in the IC cards A102 and A103, there occurs a noise as well as a disruption of synchronization at the instant that the selectors A107 and A108 operate. The error data is transferred to the next step by added to the broadcast signal. Since the IC cards A102 and A103 in the next step connected in the daisy-chain fashion or the processor such as the demultiplexer in the receiver main unit perform the broadcast signal to which the broadcast signal having the phase differences on the error data, it had a problem to cause the malfunction or loss of synchronization.
And, since it takes the time for judgement in the IC card detectors A114 and A115 in case of that the user takes the IC card off, it had problems that the it generates the error data till the IC card is take off, the unloading of the IC card is detected in the IC card detectors A114 and A115, and the controller A113 controls the selectors A107 and A108, at the same time it causes the malfunction of the circuit in the next step.
As described above, in the conventional digital broadcast receiver, a plurality of IC cards can be used to freely load to or unload from the receiver main unit. However, since the signal processor (decryptor) in the IC card requires some time for the signal processing, it disadvantageously causes a delay in inputting and outputting of signals. Accordingly, there are some amount of phase difference between the signal bypassing IC cards and the signal supplied through IC cards. When the selector selects either of the signals, there occurs a noise and/or a disruption of synchronization. The signal accompanied with the noise then propagates to later stages. Since the latter stage IC card which is connected to the leading stage IC card in the daisy-chain fashion or the signal processor such as the demultiplexer A109 in the receiving apparatus process the signal input to which the error data are added, it has a problem to cause the malfunction or the synchronization deterioration.
Then, since it takes some time for the IC card detector to determine the presence of the IC card in case that the user removes the IC card, it had problems that it causes the error, and following stages operate the malfunctions till the IC card detects that there is no IC card and the controller controls the selector.
Further, since whole signals are applied via the IC card in such a construction, there is some possibilities of problems mentioned above caused by loading or removing the IC card while the user is watching the free program signal or program signal which is using other decryption system.
The present invention has been made in view of the problem described above, and it is an object to provide a digital broadcast receiver capable of preventing the unauthorized use of signals appearing on the IC card interface portion between the receiver main unit and IC cards.
The present invention has an object to remove the drawbacks in the conventional apparatus. That is the present invention has an object to provide a digital broadcast receiver which corrects the phase difference between the broadcast signal which is carried out the signal processing by the IC card and one which is not carried out the signal processing, and prevents to generate the error data which occurs at an instance of loading/unloading of the IC card so as to prevent making the malfunction in the signal processor which is connected in daisy-chain fashion or the in the next step circuit.
Another object of the present invention is to prevent the malfunctions of IC cards or processors caused by noise or data error occurring at the time of selecting between signals output from IC cards and signals bypassing the IC cards, or at the time of removing IC cards.
A first aspect of the digital broadcast receivers according to the present invention includes, a first unit for receiving broadcast signals transmitted from a transmitter, a second unit capable of removably coupling to the first unit for applying an operation specific to the second unit to the received signal, an encryptor equipped in the first unit for encrypting the received signal and for providing the encrypted signal to the second unit, and a decryptor equipped in the first unit for decrypting the signal encrypted by the encryptor transferred through the second unit.
In the present invention, the encryptor applies the encryption to broadcast signals input to the first unit and then supplies the encrypted signals to the second unit. The first and the second units can be separated each other. It is possible to take out the input/output of the first and the second units through the IC card interface between these units but these input and output are encrypted. The output of the second unit is given to the decryptor and the encryption applied by the encryptor is decrypted.
A second aspect of the digital broadcast receivers according to the present invention includes, a disabling signal generator for detecting an ineffective portion of the broadcast signal which is supplied to each packet by added with an ineffective code which is ineffective to decode a synchronizing signal and a broadcast signal, and for generating a disabling signal at the timing that ineffective portion has been detected, at least one removable signal processor for performing a predetermined signal processing to the broadcast signal, a selector for selecting either of the broadcast signal which is directly supplied thereto or the broadcast signal which is supplied thereto after processed in the signal processor, a selector controller for controlling the selector in response to the disabling signal, and a decoder for decoding the broadcast signal supplied via the selector as ineffective one by the disabling signal.
In the digital broadcast receiver according the second aspect of the present invention, the ineffective code which is ineffective to decoding of the synchronizing signal and the broadcast signal is added to the received broadcast signall. The ineffective code in the received signal is then detected by packet basis. The disabling signal is then generated at the timing of detecting the ineffective code. In response to the disabling signal the selection controller controls the selector to select the signal directly supplied thereto or the signal supplied thereto through at least one signal processer which is removably coupled to the receiver main unit for processing the broadcast signal in a predetermined fashion. The decoder decodes the signal supplied thereto through the selector.
Accordingly, it is possible to control the selector at the signal portion which is ineffective to the nature of the original video and or audio information. It is thus possible to prevent the inconvenience that the selector causes the decoder in later stage to make the malfunction.
A third aspect of the digital broadcast receivers according to the present invention includes at least one removable second apparatus, which is connected in daisy-chain fashion via first apparatus, where the digital broadcast signal which is received and demodulated in the first apparatus or the demodulated digital broadcast signal which is obtained from outside of the first apparatus is output to the second apparatus where the signal is carried out a predetermined signal processing and again supplies the signal to the first apparatus, then the signal is decoded in the first apparatus, and further includes at least one first delay unit for outputting a bypass signal which the signal equal to the signal output to the second apparatus from the first apparatus is delayed in the first apparatus, at least one second delay unit for delaying the signal which is input to the first apparatus from the second apparatus, at least one selector for selecting the output signal supplied from the first delay unit or the second delay unit, and delay time adjuster for adjusting the delay time in the second delay unit in order that the sum of the delay time in the second apparatus and the delay time in the second delay unit will be equal to the delay time in the first delay unit.
A fourth aspect of the digital broadcast receivers according to the present invention includes at least one removable second apparatuses, which is connected in the delay-chain fashion via a first apparatus, where the digital broadcast signal which is received and demodulated in the first apparatus or the demodulated digital broadcast signal which is obtained from outside of the first apparatus is output to the second apparatus where the signal is carried out a predetermined signal processing again supplies the signal to the first apparatus, then the signal is decoded in the first apparatus, and further includes at least one selector for selecting the signal bypassing the second apparatus and the signal supplied through the second apparatus, an extractor for extracting the attribute information of the program signal from the digital broadcast signal, a determination unit for analyzing the information extracted in the extractor and determining the possibility of the necessity of the signal processing in the second apparatus, and a second controller for making the selector to select output signals from the second apparatus when the determination unit has determined that a signal processing at the second apparatus is needed.
In the digital broadcast receivers according to the third and fourth aspect of the present invention, it is possible to prevent that a noise and/or data error occurring in the stream of signals at the timing of selecting the signal directly supplied to the selector or the signal supplied to the selector through the leading second unit causes a malfunction in the latter stage second units or the first unit.
Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification.